Is it possible to opitimize Cycles' refraction material?
This might be a little bit of a late answer, but Cycles' caustics handles large light sources very well, but small ones with difficulty. I'd recommend using the Light Path node, and two lamps for every light source. One is a lamp that shines for everything that is NOT reflective/refractive. The other one is a large lamp for ONLY reflective/refractive caustics.

To do this, I'd use the Is Reflection Ray and the Is Transmission Ray outputs of the Light Path node.